The Analytical Chemistry Core will provide support in the analytical chemistry area for all projects in the proposed Program Project. The primary responsibility of this Core will be to analyze the sample submitted by the project investigators accurately and timely so that the investigators can evaluate the data with confidence before planning the next phase of their investigations. The compounds to be analyzed are retinol, retinyl-palmitate, all-trans-retinoic acid, 13-cis-retinoic acid, vitamin E, beta-carotene, lycopene, selenium, antipyrine and difluormethylornithine in human and animal plasma, skin, buccal mucosa cells, liver, and subcutaneous fat. Our assay procedures for these compounds are well established and have been published in peer-reviewed journals. In order to generate accurate and consistent data, the Core will continue to follow the extensive quality control/quality assurance program we have developed and carried out while maintaining the existing strong-tie with the National Bureau of Standards. The Core will also provide consultations to the investigators regarding the interpretation of analytical data and/or any matters related to analytical chemistry. In addition, this Core will keep abreast of current developments in the field of analytical chemistry in order to meet any special analytical problems the Core may face in the future. The laboratory of this Core is well equipped with up-to-date analytical instrument and the Principal Investigator and the staff members of the Core have extensive knowledge and experience in carrying out all the tasks mentioned above.